1. Field of the Invention
The present invention relates to a charge-transporting compound, an electrophotographic photoreceptor, an image-forming apparatus, and a process cartridge.
2. Description of the Related Art
A xerographic image-forming apparatus comprises an electrophotographic photoreceptor (hereinafter this may be referred to as “photoreceptor”), a charging device, an exposing device, a developing device and a transfer device, in which an image is formed through electrophotography with the devices.
With the recent technical development of the constitutive members and systems thereof, the xerographic image-forming apparatus that comprises a charging device, an exposing device, a developing device, a transfer device and a fixing device is being much improved for higher speed, better image quality and longer life. With that, the requirements for high-speed operability and high reliability of the respective sub-systems of the apparatus are increasing more than before. In particular, the photoreceptor for image writing thereon and the cleaning member for cleaning the photoreceptor receive more stress than any other members owing to their mutual sliding to each other, and are often scratched, worn or cracked to cause image defects. Accordingly, the requirements for high-speed operability and high reliability of these devices are severer than those of any others.
In addition, the requirement for high quality image formation is also increasing. To satisfy the requirement, the particle size of toner is reduced, the particle size distribution thereof is unified and the sphericity thereof is increased. As one type of the toner that satisfies the quality level, a chemical toner is being much developed, which is produced in a solvent consisting essentially of water. As a result, toner images that are on a photographic image level have become obtained these days.
For preventing an electrophotographic photoreceptor from being scratched or worm there is known a method of coating it with a protective layer of high mechanical strength. For example, Japanese Patent No. 3,264,218 discloses a photoreceptor coated with a protective layer that has a crosslinked structure and has a carrier transportation ability. JP-A 2002-82469 discloses a photoreceptor coated with a protective layer that contains a phenolic resin.
However, even the photoreceptors of Japanese Patent No. 3,264,218 and JP-A 2002-82469 are not always satisfactory for forming high-quality images for a long period of time for the reasons mentioned below.
The photoreceptor of Japanese Patent No. 3,264,218 may be prevented from being scratched or worn on its surface owing to the increase in the mechanical strength thereof, but on the other hand, the surface of the photoreceptor is hardly polished and the discharged products adhering to the surface of the photoreceptor are difficult to remove since the surface layer of the photoreceptor is hard. Further, when a cleaning blade presses the adhering substances to the outermost surface of the photoreceptor, then the adhering substances become more difficult to remove. As a result, oxidation-degraded substances that may be formed on the surface of the photoreceptor owing to the charging stress applied thereto may more firmly adhere to the surface of the photoreceptor. Depending on the type of the deposits and the degree of deposition on the surface of the photoreceptor, the adhering substances may lower the quality of the image formed on the photoreceptor, for example, causing white spots and density mottles in the image. As a result, the photoreceptor could not form an image of high quality.
Having investigated the photoreceptor of JP-A 2002-82469, we, the present inventors have found that the photoreceptor fails to stably form an image of high quality since its electric properties worsen depending on the condition for producing it.